It is known that most fish prefer to live in water of a given temperature. One kind of fish may prefer water of about 55 degrees, while another kind of fish may prefer water of about 70 degrees, etc. In a large body of water, such as a lake or ocean or the like, the water is in layers or strata of various temperatures. For example, the water in a stratified lake during the summer months may be at a temperature of 80 degrees near the surface while the water about fifteen to twenty feet below the surface may have a temperature of 65 to 70 degrees, and water at depths more than 20 feet may have a temperature of 60 degrees or less. Thus, the body of water, such as a lake or the like, may be considered as being divided into temperature levels or layers or strata. In limnology, temperature layers are frequently referred to as epilimnology, thermocline and hypolimnion. The thermocline is defined as a layer in which the temperature of the stratum changes at least one degree centigrade per meter of depth. It has also been found that from day to day or from week to week in a given body of water, the temperatures at various depths change, as affected by weather conditions, sub-surface current conditions, surface wind conditions, etc. It has also been found that water of a given temperature may be located a given distance below the surface at one area of a lake and water of the same temperature may be at a different distance below the surface at other areas of the lake.
Thus, fish which prefer water of a given temperature may be located at a given depth at a certain area of a lake on a certain day and at another depth a few days later. Furthermore, because of these water temperature conditions, fish which prefer water of a given temperature may be found at a given depth in one part of a lake and at another depth at another part of the lake.
Thus, it is understood that a highly desirable device for a fisherman is one which automatically maintains bait or lure or the like in water having a predetermined desired temperature, regardless of the depth involved.
Devices have been created which employ various means for maintaining an object at a given depth. However, such devices are ineffective to maintain a lure or bait in water of a predetermined desired temperature.
An object of this invention is to provide a device which seeks to maintain itself at or oscillate through a predetermined temperature stratum or layer in a body of water or other liquid which has numerous temperature strata or layers. Thus, if an appropriate type of instrument or the like is attached to the device and disposed adjacent the device, the instrument is maintained in substantially a predetermined temperature region in the body of liquid regardless of the depth of the temperature region within the limits of the device.
Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture, and the mode of operation, as will become more apparent from the following description.